1. Field of the Invention
The present invention relates to injection molding devices, and more specifically to a device to retain a slide assembly portion of an injection mold.
2. Description of the Related Art
In typical injection molds, the mold cavity is created from plates that abut each other at a parting line. When the mold is opened, these plates move apart from one another such that the molded part can be removed or ejected. In many injection molds, the mold cavity is further defined by one or more pieces that move perpendicular to the plates as the mold is opened and closed. These perpendicularly moving pieces are attached to slides which typically are moved by angle pins. The angle pin is received through an angled bore extending through the slide. In normal opening movement of the mold, the angle pin forces the slide laterally away from the molded piece along a guided path.
It is desirable to retain the slide in the retracted position to prevent unintentional slide closure. Several slide retainers are known in the art. For example, U.S. Pat. No. 3,811,645, issued to Feist (Feist retainers), discloses a slide retainer and positioner. The retainer in Feist includes a set of spring-biased jaws that grip an element, such as a pin or rod, installed on the slide when the slide is moved to the open position.
Another type of slide retainer is disclosed in U.S. Pat. No. 5,397,226, issued to Vandenberg and assigned to the D-M-E Company of Madison Heights, Mich. (Vandenberg retainers). Vandenberg retainers are characterized by a circlular body having a lip section, and a flat key section formed on one side of the lip section. A plunger having an elongated rounded plunger head is received in a cavity formed in the body. A spring is held in the cavity by a threaded plug and biases the plunger head to extend up through an opening in the top of the body. The rounded plunger head is designed to mate with a groove formed in the bottom surface of the slide.
There are several drawbacks to slide retainers based on the Feist design. First, slide retainers having different holding strengths are not of uniform size, thus if the slide designer miscalculates the required necessary holding strength, a replacement slide retainer of greater or lesser holding strength will not fit in the pocket created for the original slide retainer. Furthermore, slide retainers according to the Feist design lack adjustability, meaning different retainers must be purchased for different holding strengths. Second, these slide retaining devices require complicated machining processes to facilitate their installation. Not only does the slide retainer have to be installed into a relatively large pocket, milled into the core plate of the injection molding machine, the pin or rod also has to be installed in the slide. Any misalignment of the retainer and the pin usually results in damage to the mold and mold components. Furthermore, the large pocket into which the slide retainer is installed takes up valuable space in the injection mold.
Similarly, there are several drawbacks to slide retainers based on the Vandenberg design. First, slide retainers having different holding strengths are not of uniform size, which leads to the same problems mentioned above. Like the Feist retainers, the Vandenberg retainers lack adjustability. Additionally, the installation process for the Vandenberg retainers requires complex milling operations, such as the milling for the lip section and key sections.
In addition to the cited slide retainers, there are other types of slide retainers commercially available. However, no commercially available slide retainers utilize a live bearing, which is a bearing that allows the slide to roll over the retainer until the slide reaches the end of its travel and is secured in place by the retainer.
There remains a need for a slide retaining device that offers improved retaining properties, adjustable retaining properties, a more compact size for improved installation and greater flexibility in mold design. Furthermore, there remains a need for a slide retaining device that employs a live bearing. Additionally, there remains a need for slide retaining device components that may be used to retrofit existing devices such that the improved slide retaining devices employ a live bearing.